Influence of the Size of the Precipitates in NaCl:Pb²⁺ Crystals on Rayleigh Scattering and UV Absorption

Abstract

Using the Mie theory the extinction cross-sections of PbCI, spheres embedded in NaCl are calculated for various radii between 1 and 46 nm, in the wavelength region 220 to 400 nm. These calculations allow to propose a model with two types of spherical precipitates -the concentrations and the radii of which depend on the heat treatments -that fits the experimental results of UV absorption and Rayleigh scattering by NaCI:Pb2+ after different heat treatments.Nous avons calcule Bl'aide de la theorie de Mie les sections efficaces d'extinction de spheres de PbCI, dans NaCI, pour divers rayons compris entre 1 et 46 nm dans la region spectrale 220 it 400 nm. Ces calculs nous permettent de proposer un modele form6 de deux types de precipites spheriques -dont les concentrations et les rayons dependent de I'histoire thermique de cristal -qui rend compte quantitativement de la diffusion Rayleigh et de l'absorption UV par un cristal de NaCl dope au plomb, apres different5 traitements thermiques.

A new method of controlled doping of alkali halide crystals with Pb ions

“…At temperaturas lower than 400 ~ this effect is not so clearly evident because here £ has to expect aggregation phenomena of the Pb ions inducing changes of the absorption spectrum (e.g. [5,6]; see also Fig. 3.…”

“…At least in the case of NaC1 crystals one must be cautious using this method because the absorption spectrum related to the Pb incorporated is highly sensitive to the thermal treatment of the crystals (e.g. [2,5,6]); see also Fig. 1).…”